XV920 "Short Bus"
- Thread starter Rich Ard
- Start date
I haven't been out in the garage much the last couple weeks thanks to some adventurous bacteria that has taken up residency in my sinus cavity - and what time I had spent out there was taken up with my first customer - a guy who took a Virago 920 as payment for a drywall job and couldn't get it running. I'm thinking about having a "Virago Mechanic" shirt made up so I can hang myself from the rafters well-dressed.
Anyway...previously I had been having problems keeping the bike running on both cylinders, and thought I had pinpointed the problem to a bad coil. I picked up a pair of universal coils (note to other Virago owners - the 'universal coils' at Dime City bolt straight in to the Yamaha mounts and require only new wiring connectors) and installed them, only to find that the rear cylinder was still giving me trouble. (posted a help topic here: http://www.dotheton.com/forum/index.php?topic=50733.msg564592#msg564592)
After installing a new carb boot I opened up the valve covers - and while this bike has a fair amount of valve train noise, I was very shocked indeed to find that the valve clearance on the rear cylinder was waaaaay out of line...such that it could be measured in actual millimeters rather than hundredths or thousandths. I am not at all sure how this happened, though my guess is that I may have set valve lash at the wrong point previously.
That, of course, is where panic set in, that perhaps I had destroyed what is generally a bulletproof head - but I buttoned it all back up and the bike starts up and idles quite happily. I will find out for sure tomorrow when I roll it back off the lift and beat on it a little bit; worst case, of course, I have to get a new head, which sets me back about thirty bucks. :
I did not get the compression tester out for fear of what it might tell me.
If I understand the system correctly, though, it's unlikely that the valve clearance being too loose would cause much damage (certainly less than would come from the valves being too tight), especially in a system like this one that is pretty well-oiled.
Anyway...previously I had been having problems keeping the bike running on both cylinders, and thought I had pinpointed the problem to a bad coil. I picked up a pair of universal coils (note to other Virago owners - the 'universal coils' at Dime City bolt straight in to the Yamaha mounts and require only new wiring connectors) and installed them, only to find that the rear cylinder was still giving me trouble. (posted a help topic here: http://www.dotheton.com/forum/index.php?topic=50733.msg564592#msg564592)
After installing a new carb boot I opened up the valve covers - and while this bike has a fair amount of valve train noise, I was very shocked indeed to find that the valve clearance on the rear cylinder was waaaaay out of line...such that it could be measured in actual millimeters rather than hundredths or thousandths. I am not at all sure how this happened, though my guess is that I may have set valve lash at the wrong point previously.
That, of course, is where panic set in, that perhaps I had destroyed what is generally a bulletproof head - but I buttoned it all back up and the bike starts up and idles quite happily. I will find out for sure tomorrow when I roll it back off the lift and beat on it a little bit; worst case, of course, I have to get a new head, which sets me back about thirty bucks. :
I did not get the compression tester out for fear of what it might tell me.If I understand the system correctly, though, it's unlikely that the valve clearance being too loose would cause much damage (certainly less than would come from the valves being too tight), especially in a system like this one that is pretty well-oiled.
Rich Ard said:I haven't been out in the garage much the last couple weeks thanks to some adventurous bacteria that has taken up residency in my sinus cavity - and what time I had spent out there was taken up with my first customer - a guy who took a Virago 920 as payment for a drywall job and couldn't get it running. I'm thinking about having a "Virago Mechanic" shirt made up so I can hang myself from the rafters well-dressed.
Anyway...previously I had been having problems keeping the bike running on both cylinders, and thought I had pinpointed the problem to a bad coil. I picked up a pair of universal coils (note to other Virago owners - the 'universal coils' at Dime City bolt straight in to the Yamaha mounts and require only new wiring connectors) and installed them, only to find that the rear cylinder was still giving me trouble. (posted a help topic here: http://www.dotheton.com/forum/index.php?topic=50733.msg564592#msg564592)
After installing a new carb boot I opened up the valve covers - and while this bike has a fair amount of valve train noise, I was very shocked indeed to find that the valve clearance on the rear cylinder was waaaaay out of line...such that it could be measured in actual millimeters rather than hundredths or thousandths. I am not at all sure how this happened, though my guess is that I may have set valve lash at the wrong point previously.
That, of course, is where panic set in, that perhaps I had destroyed what is generally a bulletproof head - but I buttoned it all back up and the bike starts up and idles quite happily. I will find out for sure tomorrow when I roll it back off the lift and beat on it a little bit; worst case, of course, I have to get a new head, which sets me back about thirty bucks. :
If I understand the system correctly, though, it's unlikely that the valve clearance being too loose would cause much damage (certainly less than would come from the valves being too tight), especially in a system like this one that is pretty well-oiled.
"Loose" clearances only cause damage to your hearing ! Long term of course not good due to the hammering effect rather than a wiping effect. Tight clearances on the other hand can lead to burned valves.
In another lifetime I briefly worked as a sales manager for a major Motorcycle dealer in Birmingham [UK]. Our agency included Moto-Guzzi. I sold a brand new California which went through the normal PDI system.
The customer brought it back after 2 days with one exhaust pipe seriously blued up. I was the first to see it [ as I'd sold it ! ]. Immediately I suspected a tight valve clearance. I took it up the road and sure enough it was down on power. I passed the info. on to the workshop, and they all promptly fell about laughing - what would a mere "salesman" know ! Sure enough, the one cyclinder was way too tight on clearance. Did that make me a god in their eyes ? Well no - they got the hump as the owner found out and gave them loads of grief !!
mydlyfkryzis
当有疑问时踢你的敌人在生殖器上，你可以道歉后
Put a Honda Engine in there with Hydraulic Adjusters, you'll never adjust the valves again.... 8)
I heard from someone who will remain nameless, but he said if you powder coat the coils, they will work much better.... ;D
I heard from someone who will remain nameless, but he said if you powder coat the coils, they will work much better.... ;D
crazypj
Split personality, I fake being smart
Honda hydraulic adjusters work great - when they work. I've had issues with the CBX750 plus various others
I've spent way too much time doing development work for Honda that they should have done before the damn things went to market. The V-4's are awful bikes, even the gear driven ones. I think they may have fixed the 800 but the 750's and 1100's SUCKED
I've spent way too much time doing development work for Honda that they should have done before the damn things went to market. The V-4's are awful bikes, even the gear driven ones. I think they may have fixed the 800 but the 750's and 1100's SUCKED
Evorussell
Active Member
Care to share a copy of that wiring diagram you have under your voltage regulator/rectifier?
Trying to figure out how/why it has so many wires, when I only need 3....haha
Trying to figure out how/why it has so many wires, when I only need 3....haha
Evorussell
Active Member
At PJ's suggestion I am switching from a Koehler style reg/rec to a MOSFET style(running an anti-gravity battery).
The one you are using is one of the best price wise, but I like to fully understand what I am getting into, and I can't wrap my head around the 7? wires coming out of it.
The one you are using is one of the best price wise, but I like to fully understand what I am getting into, and I can't wrap my head around the 7? wires coming out of it.
Wonder why my crankcase is full of cam chain tensioner.
Working theory: rear head cam chain tensioner broke (along with a bit of cast aluminium, so it's time for a new cylinder) and a piece jammed in the starter idler gears.
I had opened up the sidecover to work on the starter clutch assembly and this was definitely not what I had planned on.
Working theory: rear head cam chain tensioner broke (along with a bit of cast aluminium, so it's time for a new cylinder) and a piece jammed in the starter idler gears.
I had opened up the sidecover to work on the starter clutch assembly and this was definitely not what I had planned on.
crazypj
Split personality, I fake being smart
Could be
all V twins, because of the firing intervals, have the cam 'drive' the crank at certain positions when valve spring pressure is closing valve
With real loose valve clearance, the cam has the ability to spin further before crank takes over again.
I've never seen an XV do damage but, early CX 500 was known to break the tensioner bosses off the crankcase, Honda had several major modifications to tensioners over a 3~4 yr period. (the last one, fully automatic, lasted at least 18,000miles before it started giving problems and needed changing)
The problem is actually a LOT worse if bike is used at low rpm, at higher rpm (~4,000+) there just isn't as much time available for things to change direction
all V twins, because of the firing intervals, have the cam 'drive' the crank at certain positions when valve spring pressure is closing valve
With real loose valve clearance, the cam has the ability to spin further before crank takes over again.
I've never seen an XV do damage but, early CX 500 was known to break the tensioner bosses off the crankcase, Honda had several major modifications to tensioners over a 3~4 yr period. (the last one, fully automatic, lasted at least 18,000miles before it started giving problems and needed changing)
The problem is actually a LOT worse if bike is used at low rpm, at higher rpm (~4,000+) there just isn't as much time available for things to change direction
Re: Re: XV920 "Short Bus"
This is my major concern - that the chunks of Al in my crankcase are from the case and not the cylinder.
I'm going to tear the head off a 750 motor i have here to see if i can figure out what's what. Working on a couple avenues for a 920 motor i can 'drop' in so i can get back on the road.
crazypj said:
This is my major concern - that the chunks of Al in my crankcase are from the case and not the cylinder.
I'm going to tear the head off a 750 motor i have here to see if i can figure out what's what. Working on a couple avenues for a 920 motor i can 'drop' in so i can get back on the road.
Well, beats me.
I pulled the rear cylinder off of an XV750 parts motor to examine the cam chain guide and see if what came out of my oil pan was the boss for the cam chain guide, and it wasn't. I have no idea where this came from - looks kind of like an oil guiding fin.
I did find all the rest of the guide.
Motor turns just fine; rolls through the gears, no problem. I ordered a gasket kit - am going to pull the motor, install a new cam chain guide, and bolt it back together. I will keep on the lookout for a second engine so that I have one in hand if it turns out that I'm wrong - I realize that in a perfect world, I would gut the motor and figure out where this came from, but I appear to have all of what broke off, and it wasn't holding anything else in place.
So - working theory is that my extraordinarily loose valve clearance, over the course of 2500 miles, destroyed the cam chain guide; in making its way down from the cylinder, the guide took out a piece of aluminium; one of these things jammed the starter motor, burning it out.
Dreadrock - if this thing isn't put back together by the weekend I'm strapping it down in my van and finishing up at your house.
I pulled the rear cylinder off of an XV750 parts motor to examine the cam chain guide and see if what came out of my oil pan was the boss for the cam chain guide, and it wasn't. I have no idea where this came from - looks kind of like an oil guiding fin.
I did find all the rest of the guide.
Motor turns just fine; rolls through the gears, no problem. I ordered a gasket kit - am going to pull the motor, install a new cam chain guide, and bolt it back together. I will keep on the lookout for a second engine so that I have one in hand if it turns out that I'm wrong - I realize that in a perfect world, I would gut the motor and figure out where this came from, but I appear to have all of what broke off, and it wasn't holding anything else in place.
So - working theory is that my extraordinarily loose valve clearance, over the course of 2500 miles, destroyed the cam chain guide; in making its way down from the cylinder, the guide took out a piece of aluminium; one of these things jammed the starter motor, burning it out.
Dreadrock - if this thing isn't put back together by the weekend I'm strapping it down in my van and finishing up at your house.
